An imaging probe (102) for use in measuring surface roughness by angular speckle correlation is shown. The imaging probe comprises a first illumination fibre (201) to illuminate a sample location (103) on a surface, and having an input end for coupling of coherent light into the fibre, and an output end cleaved at an angle θ1, a second illumination fibre (202) to illuminate the sample location on the surface, and having an input end for coupling of coherent light into the fibre, and an output end cleaved at an angle θ2 that is different from θ1, and an image transmission system (204) for transmission of a speckle pattern caused by illumination of the sample location on the surface by coherent light from either the first illumination fibre or the second illumination fibre.